INK JET PRINTER NOZZLE ASSEMBLY

Abstract: A nozzle assembly for an ink jet printer has a nozzle mounted in a stepped bore (4) in a supporting nozzle plate (1). The nozzle (7) is disposed on a supporting shoulder within the stepped bore and is sealed thereto by a resilient seal ring (6) disposed between the nozzle and the shoulder. The nozzle is retained in the stepped bore by a crimp (9) of the nozzle plate surface.

Description: INK JET PRINTER NOZZLE ASSEMBLY The present invention relates to an ink jet printer nozzle assembly of the type comprising one or more nozzles mounted in a nozzle plate. Nozzle assemblies of this type are well known and usually comprise a jewel nozzle in which an orifice is formed to a required shape and dimensions and a nozzle- supporting plate having a stepped bore into which the nozzle is fixed by means of adhesive. Adhesive is used in order to assure a permanent, rigid attachment of the nozzle in the nozzle plate. However, there are disadvantages in using this type of fixing. For example, adhesive may enter the nozzle orifice or the narrower portion of the stepped bore in the nozzle plate and thus impede the desired flow through it. Furthermore, the adhesive forms a layer between the underside of the nozzle and the shoulder in the stepped bore in the nozzle plate and it is difficult to control, to the desired degree of accuracy, the precise positioning of the nozzle, as a result. Accuracy of position is important and particularly so in regard to ensuring that the emitted ink jet is normal to the surface of the nozzle plate. According to the present invention therefore, there is provided a nozzle assembly for an ink jet printer, the nozzle assembly comprising a nozzle mounted in a stepped bore in a supporting nozzle plate, the nozzle being disposed on a supporting shoulder within the stepped bore, sealed thereto by a resilient seal ring disposed between the nozzle and the shoulder, and retained therein by a crimp of the nozzle plate surface. The invention also includes a method of manufacturing a nozzle assembly of this type, in which the nozzle is disposed on a supporting shoulder within the stepped bore of the nozzle plate, a resilient seal ring is provided between the shoulder and the nozzle, and the nozzle is retained within the stepped bore by crimping of the nozzle plate surface around the open end of the stepped bore. The seal ring preferably comprises a seal ring which is formed of FTFE or other similar compliant material, to provide a secure seal between the underside of the nozzle and the shoulder in the stepped bore. Alternatively, the shoulder may include a retained seal disposed, for example in an annular groove in the shoulder or the adjacent wall of the bore. The use of a PTFE seal ensures a sufficiently secure seal to avoid leakage around the nozzle in use, avoiding the need for adhesive to be used in fixing and sealing the nozzle in the nozzle plate. Crimping the nozzle in position enables the problems associated with adhesive fixing to be overcome and, in particular, enables the nozzle to be accurately positioned in parallelism with the nozzle plate to ensure the precise location of the jet of ink which issues therefrom in use. The nozzle may be initially held in position within the stepped bore by a cylindrical guide around which an annular crimping tool may slide, so as to be driven against the edge of the open end of the bore around the nozzle, to produce the crimp. One example of a nozzle assembly according to the present invention will now be described with reference to the accompanying drawings, in which:- Fig. 1 is a side elevation, partly sectioned, of a nozzle plate and printing tool; Fig. 2 is an enlarged view of the crimp head of a crimping tool; Fig. 3 is an enlarged view of a location pin for locating the plate relative to the tool; and. Fig. 4 is a plan view of the PTFE seal. Figure 1 shows a nozzle plate 1 positioned on the base plate 2 of a crimping tool, the base plate 2 having a hardened steel locating pin 3 which locates within a bore 4 formed in the nozzle plate. Coaxial with the bore 4 is an enlarged counterbore 5 in which are positioned firstly a PTFE seal 6 and a jeweled nozzle 7 having a tapered central orifice 8. Figure 1 shows the finished nozzle plate, after crimping of the jewel 7 into position in the counterbore 5 has taken place, an annular crimp 9 being shown. In order to form the crimp 9 a cylindrical guide 10 is first lowered into position on top of the jewel 7 and thereafter the annular crimping head 11 of the crimping tool is thrust downwardly around the cylindrical guide 10 into engagement with the upper surface 12 of the nozzle plate immediately around the end of the counterbore 5 in order to form the crimp. PTFE seal 6 supports the jewel or nozzle in the counterbore 5 at a predefined position so that the nozzle or jewel 7 is always fixed in the same relative position within the nozzle plate, thus ensuring consistency of dimensions across different nozzle assemblies. The shape of the end of the annular crimping head 11 is more clearly seen in figure 2 and the form of the locating pin 3 seen in more detail in figure 3. The PTFE seal itself is shown in figure 4.

Claims: CLAIMS 1. A nozzle assembly for an ink jet printer, the nozzle assembly comprising a nozzle mounted in a stepped bore (4) in a supporting nozzle plate (1) , the nozzle (7) being disposed on a supporting shoulder within the stepped bore, sealed thereto by a resilient seal ring (6) disposed between the nozzle and the shoulder, and retained therein by a crimp (9) of the nozzle plate surface. 2. A nozzle assembly according to claim 1, wherein the seal ring comprises a separate seal ring (6) formed from a compliant material, to provide a secure seal between the underside of the nozzle (7) and the shoulder in the stepped bore (4). 3. A nozzle assembly according to claim 2, wherein the seal ring (6) is formed from PTFE or other similar material. 4. A nozzle assembly according to claim 1, wherein the shoulder includes a retained seal disposed in an annular groove on the shoulder or adjacent wall of the bore. 5. A method of manufacturing a nozzle assembly in which the nozzle (7) is disposed on a supporting shoulder within a stepped bore (4) of a nozzle plate (1), a resilient seal ring is provided between the shoulder and the nozzle, and is retained within the stepped bore by crimping of the nozzle plate surface around the open end of the stepped bore. 6. A method according to claim 5, wherein the nozzle (7) is initially held in position within the stepped bore (4) by a cylindrical guide around which an annular crimping tool (11) may slide, so as to be driven against the edge of an open end of the bore around the nozzle, to produce the crimp (9) .

Inventors: CHAMBERLAIN COLIN EDWARD, LECHEHEB AMMAR, PALMER DANNY CHARLES, ZABA JERZY, CHAMBERLAIN, COLIN, EDWARD, LECHEHEB, AMMAR, PALMER, DANNY, CHARLES, ZABA, JERZY
Applicants: CHAMBERLAIN COLIN EDWARD, DOMINO PRINTING SCIENCES PLC, LECHEHEB AMMAR, PALMER DANNY CHARLES, ZABA JERZY, CHAMBERLAIN, COLIN, EDWARD, LECHEHEB, AMMAR, PALMER, DANNY, CHARLES, ZABA, JERZY
Application year: 1994
Main classification: B41J2
IPC codes: B41J2